A nearly complete hominid skeleton has been found in the lowest fossil-bearing layers of South Africa's Sterkfontein Cave. Discovered by paleontologist Ron Clarke and Sterkfontein fossil specialists Nkwane Molefe and Stephen Motsumi, the remains of the four-foot-tall individual, estimated to be 3.2 to 3.6 million years old, are the most complete australopithecine skeleton found to date. The first fossils of the skeleton, known as StW-573, came to light in 1994, when Clarke happened upon four left foot bones while searching through animal remains in Sterkfontein's storage shed. Clarke subsequently found the rest of the foot, parts of a left lower leg, and fragments of a right tibia in a storage vault at the University of the Witwatersrand, in Johannesburg, where cataloged finds from Sterkfontein are kept.

Suspecting that more of the skeleton might still be preserved in the western part of the cave, where the other fragments had been recovered, Clarke and his team began reinvestigating the site in 1997, finding the rest of the skeleton still embedded in the limestone by May 1998.

"What is particularly interesting is just how primitive the specimen is," says Clarke, noting the flexibility of the joints in the skeleton's feet. "While we know that australopithecines were bipedal by this date," he adds, "the architecture of StW-573's feet suggests that this individual was also capable of grasping limbs and climbing trees like a chimpanzee."

While taxonomic identification must await the full excavation of the skeleton, expected to take a year or more, paleontologists such as Randall Susman of the State University of New York, who examined the original foot bones as well as some of the newly discovered material, suspect that the skeleton may be of the species Australopithecus afarensis, the same as the 3.2 million-year-old Lucy, found in Ethiopia in 1974, or a South African variant or subspecies. If so, StW-573 attests the species' presence outside of East Africa and suggests it may have played a greater role in early hominid evolution than if it were geographically restricted.

If, on the other hand, the specimen belongs to Australopithecus africanus, well known in South Africa from specimens like the 2.3-million-year-old Taung child and a 2.5-million-year-old male from a later stratum at Sterkfontein, it will be the oldest example found to date. A. africanus has been thought to have thrived between 2.5 and 3.0 million years ago.